              (process-token [2/3 5/6] :+) => [3/2]
              (process-token [0 0] :+) => [0]
              )
+       (fact "process-token with :+ and many numbers"
+             (process-token [5 8 9 6 3 2] :+) => [5 8 9 6 5])
        )
 
 (facts "about process-token with :-"

             (process-token [2/3 5/6] :-) => [-1/6]
             (process-token [0 0] :-) => [0]
             )
       )

(facts "about process-token with :÷"

       (fact "process-token with :swap and only one number"
             (process-token [7] :swap) => [7])
       (fact "process-token with :swap and two numbers"
             (process-token [3 5] :swap) => [5 3])
       (fact "process-token with :swap and several numbers"
             (process-token [5 8 9 6 3 2 0] :swap) => [5 8 9 6 3 0 2]))

(facts "about process-token with a variable"
       (fact "process-token with an undefined variable"
